I'm moving to Corvallis, OR next week. I know that Portland & Western Railroad runs in the middle of Corvallis. But is there anyone knows the approximate schedule of P&W, or at least which time of day is the busiest to see those trains in Corvallis?

A good source of info is the Portland & Western Railroad discussion group on Yahoo.

I believe that the Toledo Hauler runs westbound in the late afternoon/evening; eastbound is at night. There is a Corvallis Switcher that works out of Albany but I'm not sure of the schedule. The Westsider I believe also runs through Corvallis Junction (north end of town, but not through downtown) in the afternoon/evening and returns in the morning.

The Albany & Eastern has a GP-9 that works the former "Lower Westside" (a.k.a. Bailey Branch) under contract to Vernell Farms which now owns the railroad south of Corvallis; it seems to run on an as-needed basis. But they don't run north of the yard and onto 6th Street.